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<title>FISTTP—Store Integer with Truncation </title></head>
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<h1>FISTTP—Store Integer with Truncation</h1>
<table>
<tr>
<th>Opcode</th>
<th>Instruction</th>
<th>64-Bit Mode</th>
<th>Compat/Leg Mode</th>
<th>Description</th></tr>
<tr>
<td>DF /1</td>
<td>FISTTP <em>m16int</em></td>
<td>Valid</td>
<td>Valid</td>
<td>Store ST(0) in <em>m16int with truncation.</em></td></tr>
<tr>
<td>DB /1</td>
<td>FISTTP <em>m32int</em></td>
<td>Valid</td>
<td>Valid</td>
<td>Store ST(0) in <em>m32int with truncation.</em></td></tr>
<tr>
<td>DD /1</td>
<td>FISTTP <em>m64int</em></td>
<td>Valid</td>
<td>Valid</td>
<td>Store ST(0) in <em>m64int</em> with truncation.</td></tr></table>
<h2>Description</h2>
<p>FISTTP converts the value in ST into a signed integer using truncation (chop) as rounding mode, transfers the result to the destination, and pop ST. FISTTP accepts word, short integer, and long integer destinations.</p>
<p>The following table shows the results obtained when storing various classes of numbers in integer format.</p>
<h3>Table 3-28.  FISTTP Results</h3>
<table>
<tr>
<th>ST(0)</th>
<th>DEST</th></tr>
<tr>
<td>− ∞  or  Value Too Large for DEST Format</td>
<td>*</td></tr>
<tr>
<td>F ≤  − 1</td>
<td>− I</td></tr>
<tr>
<td>− 1 &lt; F &lt; + 1</td>
<td>0</td></tr>
<tr>
<td>F Š + 1</td>
<td>+ I</td></tr>
<tr>
<td>+ ∞  or Value Too Large for DEST Format</td>
<td>*</td></tr>
<tr>
<td>NaN</td>
<td>*</td></tr></table>
<p><strong>NOTES:</strong></p>
<p>F Means finite floating-point value.</p>
<p>Ι</p>
<p>Means integer.</p>
<p>∗ Indicates floating-point invalid-operation (#IA) exception.</p>
<p>This instruction’s operation is the same in non-64-bit modes and 64-bit mode.</p>
<h2>Operation</h2>
<pre>DEST ←  ST;
pop ST;</pre>
<h2>Flags Affected</h2>
<p>C1 is cleared; C0, C2, C3 undefined.</p>
<h2>Numeric Exceptions</h2>
<p>Invalid, Stack Invalid (stack underflow), Precision.</p>
<h2>Protected Mode Exceptions</h2>
<table class="exception-table">
<tr>
<td>#GP(0)</td>
<td>
<p>If the destination is in a nonwritable segment.</p>
<p>For an illegal memory operand effective address in the CS, DS, ES, FS or GS segments.</p></td></tr>
<tr>
<td>#SS(0)</td>
<td>For an illegal address in the SS segment.</td></tr>
<tr>
<td>#PF(fault-code)</td>
<td>For a page fault.</td></tr>
<tr>
<td>#AC(0)</td>
<td>If alignment checking is enabled and an unaligned memory reference is made while the current privilege level is 3.</td></tr>
<tr>
<td>#NM</td>
<td>
<p>If CR0.EM[bit 2] = 1.</p>
<p>If CR0.TS[bit 3] = 1.</p></td></tr>
<tr>
<td>#UD</td>
<td>
<p>If CPUID.01H:ECX.SSE3[bit 0] = 0.</p>
<p>If the LOCK prefix is used.</p></td></tr></table>
<h2>Real Address Mode Exceptions</h2>
<table class="exception-table">
<tr>
<td>GP(0)</td>
<td>If any part of the operand would lie outside of the effective address space from 0 to 0FFFFH.</td></tr>
<tr>
<td>#NM</td>
<td>
<p>If CR0.EM[bit 2] = 1.</p>
<p>If CR0.TS[bit 3] = 1.</p></td></tr>
<tr>
<td>#UD</td>
<td>
<p>If CPUID.01H:ECX.SSE3[bit 0] = 0.</p>
<p>If the LOCK prefix is used.</p></td></tr></table>
<h2>Virtual 8086 Mode Exceptions</h2>
<table class="exception-table">
<tr>
<td>GP(0)</td>
<td>If any part of the operand would lie outside of the effective address space from 0 to 0FFFFH.</td></tr>
<tr>
<td>#NM</td>
<td>
<p>If CR0.EM[bit 2] = 1.</p>
<p>If CR0.TS[bit 3] = 1.</p></td></tr>
<tr>
<td>#UD</td>
<td>
<p>If CPUID.01H:ECX.SSE3[bit 0] = 0.</p>
<p>If the LOCK prefix is used.</p></td></tr>
<tr>
<td>#PF(fault-code)</td>
<td>For a page fault.</td></tr>
<tr>
<td>#AC(0)</td>
<td>For unaligned memory reference if the current privilege is 3.</td></tr></table>
<h2>Compatibility Mode Exceptions</h2>
<p>Same exceptions as in protected mode.</p>
<h2>64-Bit Mode Exceptions</h2>
<table class="exception-table">
<tr>
<td>#SS(0)</td>
<td>If a memory address referencing the SS segment is in a non-canonical form.</td></tr>
<tr>
<td>#GP(0)</td>
<td>If the memory address is in a non-canonical form.</td></tr>
<tr>
<td>#NM</td>
<td>CR0.EM[bit 2] or CR0.TS[bit 3] = 1.</td></tr>
<tr>
<td>#MF</td>
<td>If there is a pending x87 FPU exception.</td></tr>
<tr>
<td>#PF(fault-code)</td>
<td>If a page fault occurs.</td></tr>
<tr>
<td>#AC(0)</td>
<td>
<p>If alignment checking is enabled and an unaligned memory reference is made while the current privilege level is 3.</p>
<p>If the LOCK prefix is used.</p></td></tr></table></body></html>